The objective of this study is to access renal function in renal transplant patients. Here kidney function is determined by administering renal markers--PAH, Iothalamate and Cephalexin to renal transplant patients to study active tubular anionic secretion, filtration, and active tubular secretion. Twelve kidney transplant patients will be divided into two groups, six will receive Iothalamate (IOH) and PAH over a three hour period, the other six will receive Cephalexin as a bolus and studied over eight hours. Drugs will be assayed in plasma and urine collected, and results compared with six normals receiving Ioth/PAH.